Biodegradable materials have long been studied for their applicability in commonly-used products. Recently, increased emphasis has been placed on developing products made from biodegradable materials as replacements for existing, non-biodegradable products. In fact, some governmental regulations call for the phasing out of certain non-biodegradable products in lieu of biodegradable counterparts.
The changeover to the utilization of biodegradable materials in such products, however, has been met with both implementation challenges, as well decreased performance issues. Furthermore, products fabricated from biodegradable materials have typically been more expensive than conventional non-biodegradable products. Such issues have limited the extent to which products fabricated from biodegradable materials have been widely accepted in residential or industrial applications alike.
A particular example of a product that is well suited for the use of biodegradable material is a bag, such as those commonly used and/or sold at grocery stores, or temporary refuse containers, and the like. Recently, certain municipalities have required the use of biodegradable bags. To qualify as “biodegradable”, materials forming the biodegradable product must have at least a 90% conversion rate of starting material to CO2 and water within six months of disposal thereof. Bags and other containers fabricated from biodegradable materials that have been utilized to date, however, do not perform as well strengthwise as conventional products, and are typically more expensive than such conventional products.
A specific drawback to currently available containers, more particularly bags, fabricated from biodegradable materials is the low strength characteristics associated with such materials. Accordingly, currently available biodegradable containers are undesirably weak, in that such products are substantially stretchable under relatively low forces.
To date, efforts in creating viable and economical fully biodegradable materials have focused primarily on blending known biodegradable polymeric resins such as polyesters with starch to reduce the cost. A popular blend is a resin mixture called Mater-Bi produced and sold by Novamont. Bags made from the Mater-Bi material are widely available, but have substantial physical drawbacks such as low elongation resistance, low puncture resistance, and poor moisture resistance.
Two primary problems to be overcome in order to increase acceptance and use of biodegradable products are strength and price. Polyethylene, one of the most commonly used polymeric resins base for non-biodegradable films used in the manufacture of, for example, bags, is a low cost resin that is versatile enough to handle the physical requirements of any disposal bags. Polyethylene bags are also typically less expensive than their biodegradable counterparts. Such characteristics of polyethylene represent a marketing barrier to the acceptance of similar biodegradable products.
We have surprisingly found that commonly-utilized biodegradable polymeric resins can be blended with a polylactic acid to produce substantially stronger fully biodegradable films than those presently available. A particular characteristic of the resulting films is reduced elongation under load. Thus, the blends of the present invention enable the production of substantially more durable bags. In addition, the fully biodegradable films of the present invention are typically less costly to produce than currently manufactured biodegradable films. Such factors are important in increasing acceptance of biodegradable containers in environmental programs worldwide.
Lactic acid polymers have been extensively investigated for many years. Primarily, attention has been focused on the biodegradable aspects of such lactic acid polymers. A great deal of work in the last twenty years centered on the medical use of these polymers, upon which many patents have issued. A patent related to uses for polylactic acid is U.S. Pat. No. 6,323,307, issued to Cargill Dow Polymers on Nov. 27, 2001.
Other patents relating to the use of polylactic acid include U.S. Pat. Nos. 5,216,050 and 5,444,113. Such patents generally describe polylactic acid polymers that can be blended or plasticized with internal or external plasticizers.
The invention of the present application describes a simple straightforward method of using PLA to produce a useful product for a rapidly growing environmental problem. The bags of the present application are unexpectedly tougher, stronger, can handle much heavier loads, and use less resin than conventional biodegradable bags currently available.
It is therefore a primary object of the present invention to provide fully biodegradable materials in film form having strength characteristics similar to that of polyethylene film.
It is a further object of the present invention to provide biodegradable bags formed from one or more fully biodegradable films having strength and durability characteristics similar to that of conventional polyethylene films.
It is another object of the present invention to provide economical fully biodegradable films having enhanced strength and durability characteristics.
It is a still further object of the present invention to provide fully biodegradable films comprising a blended product of polylactic acid and a suitable biodegradable polymeric resin, such as a polyester.
It is a yet further object of the present invention to provide fully biodegradable films comprising a blended product of about 30% by weight polylactic acid and about 70% by weight of a suitable biodegradable polymeric resin.
It is another object of the present invention to provide a biodegradable bag being formed from one or more fully biodegradable blown films, which films are a blended product of polylactic acid and a suitable biodegradable polymeric resin.
It is another object of the present invention to provide a fully biodegradable bag formed from one or more biodegradable films having a caliper thickness of about 2 mils or less.